CEM Renewable Energy and Cogeneration 2 — Questions and Answers
Question 1: A fuel cell generates electricity through:
- Combustion of hydrogen with oxygen in a pressurized chamber
- Electrochemical reaction of fuel and oxidant without combustion, producing electricity and heat (Correct answer)
- Photovoltaic conversion of solar energy
- Mechanical rotation of a generator driven by fuel expansion
Correct answer: Electrochemical reaction of fuel and oxidant without combustion, producing electricity and heat
Fuel cells convert chemical energy directly to electricity via electrochemical reactions (no combustion), achieving higher efficiencies (40-60%) and producing heat as a recoverable byproduct.
Question 2: The overall efficiency of a CHP system is calculated as:
- Electrical output only divided by fuel input
- (Electrical output + recovered heat output) divided by total fuel input (Correct answer)
- Electrical output divided by (fuel input − heat losses)
- Heat output only divided by fuel input
Correct answer: (Electrical output + recovered heat output) divided by total fuel input
CHP overall efficiency counts both useful electrical and thermal outputs, expressing total useful energy recovered as a fraction of fuel consumed.
Question 3: Levelized Cost of Energy (LCOE) for a renewable project is useful because it:
- Measures the peak power output on the best production day
- Expresses the average cost per kWh over the project lifetime, enabling comparison with utility rates (Correct answer)
- Calculates the annual O&M cost divided by capacity in kW
- Determines federal tax credit eligibility for the project
Correct answer: Expresses the average cost per kWh over the project lifetime, enabling comparison with utility rates
LCOE normalizes all project costs (capital, O&M, financing) over lifetime energy production, providing a comparable cost-per-kWh metric for evaluating against utility rates or alternative generation.
Question 4: The Investment Tax Credit (ITC) for solar energy systems in the US allows eligible projects to:
- Deduct installation labor costs from project timeline
- Claim a percentage of the installation cost as a direct federal income tax credit (Correct answer)
- Receive cash payments from the utility for excess generation
- Depreciate solar assets over 40 years for tax purposes
Correct answer: Claim a percentage of the installation cost as a direct federal income tax credit
The ITC allows commercial and residential solar owners to claim a percentage of the total system cost (currently 30% under the Inflation Reduction Act) as a direct federal tax credit.
Question 5: In a PV system, the maximum power point tracker (MPPT) in the inverter serves to:
- Limit panel output to protect the inverter from overload
- Continuously adjust operating voltage to extract maximum power from panels under varying conditions (Correct answer)
- Convert AC power from the grid to DC for battery storage
- Monitor and report panel-level faults to the monitoring system
Correct answer: Continuously adjust operating voltage to extract maximum power from panels under varying conditions
MPPT algorithms dynamically adjust the DC operating point of the PV array to continuously operate at the voltage/current combination yielding maximum power as irradiance and temperature change.
Question 6: Interconnection requirements for distributed generation systems are primarily managed by:
- The US Department of Energy national laboratory system
- The local electric utility or grid operator under IEEE 1547 and state-specific interconnection standards (Correct answer)
- The building owner without utility involvement
- ASHRAE standards for on-site generation
Correct answer: The local electric utility or grid operator under IEEE 1547 and state-specific interconnection standards
Utilities manage interconnection under IEEE 1547 (Standard for Interconnection of Distributed Energy Resources) and state commission-approved tariffs, requiring technical review and protective relaying.
CEM Renewable Energy and Cogeneration 2
A fuel cell generates electricity through: